By means of such interfaces it is possible to transmit to a lamp operating device signals from a bus or from a button or switch connected with the mains voltage. Thereby there is usually provided in the interface an evaluation logic which transforms the digital or analog signals present at the inputs of the interface into control signals for the lamp operating device. The signals delivered to the interface may represent commands (desired values for setting values etc.) but also condition-related information. In particular if a bi-directional interface is provided, condition information from the lamp operating device can be transmitted to a bus connected at the interface.
Such interfaces are employed for example in the context of the so-called DALI (Digital Adressable Lightening Interface) industry standard.
From DE 197 57 295 A1 (see there FIG. 7) there is known an example for an interface to which there can be selectively applied signals from a button/switch or rather digital signals from a bus. In the case of a connected button, a connected electronic ballast can then for example be switched on or switched off by means of a pressing of the button. Further, by means of an appropriate temporal duration of the pressure actuation of the button a desired value for a brightness regulation can be attained, since the connected evaluation logic of the interface transforms the duration of the pressure actuation of button into a desired value signal for the electronic ballast (EVG).
As is schematically illustrated in FIG. 6, there is provided between the input-side terminals 1, 2 of such an interface 12 and the operating device 13 for one or more lamps 14, an electrical isolation element 4, such as for example an optocoupler. The digital signals, for example, delivered from a bus, are transmitted via this electrical isolation element to the evaluation logic 3, which thus, seen from the bus, is located behind the electrical isolation element 4. Since on the other hand, the evaluation logic 3 must react immediately to incoming signals from the terminals of the interface, with the state of the art there is the problem that the lamp operating device can never be completely switched off, since otherwise also the evaluation logic would be switched off. The evaluation logic must thus be continuously supplied with mains voltage 15, which manifests itself in corresponding stand-by losses (power which is used in stand-by operation).
FIG. 7 shows schematically how the current/voltage supply 27 for the evaluation logic 3 in the ballast 13 resorts to the mains supply 15 of the ballast 13 by means of an AC/DC converter 16. Further, there can be seen also schematically in the ballast 13, the inverter 17, the output driver for the lamp(s) 4 and the lamp control/regulation 19 communicating bi-directionally with the evaluation logic 3.
The stand-by losses stand in contradication to the enormous efforts which have been undertaken in recent times in the matter of energy saving in lamp technology. As an example WO 02/082618 A1 is mentioned, which shows a possibility for reducing the stand-by losses in the case of a DALI interface. In accordance with this state of the art, a DALI processor is put into a stand-by mode when no signals are transmitted on the connected DALI bus. Further, FIG. 3 of WO 02/082618 A1 shows an example for the generally prevailing trend that the evaluation logic, seen from the DALI bus, must be arranged behind the electrical isolation element (isolation 310 in FIG. 3).
From U.S. Pat. No. 6,388,399 there is known a control system for the control of a plurality of consuming units arranged in a distributed manner, in which control units are provided for the control of the consuming units associated with them. The possibility of brightness control of lamps is opened up in that through the control units in each case a control signal between 0 and 10 Volts, corresponding to a desired brightness, is generated, which is then transformed by a lamp operating device connected downstream of the control unit for the operation of a lamp. The configuration of the 0-10 Volt interface needed for the transformation of the control signals, is however, not described in detail.
The present invention now addresses the object of reducing the stand-by losses in an interface for a lamp operating device.
This object is achieved by means of the features of the independent claims. The dependent claims further develop the central concept of the invention in particularly advantageous manner.